I used to live in Hertfordshire and I now have experience of Bills work, Nicki's work, and also a local flash mapper who has since gone bust.
My stage 1 map was done by ChippedUK and was a straight forward flash with no logs or anything like that. It felt great to start with and I was well happy.
A few years later I ended up heading to see Bill for a rollin road session. The map I had turned out to be a **** and the fueling was really really bad. Bill flashes on a stage 1 revo and tweaked the boost and fuel to get te best out of my car. Turbo was tired and the car couldn't produce more then 250bhp.
I removed my turbo and sent it off to be refurbished. Turns out its wrecked and unrepairable. This was a result of the poor fueling from the original map. New turbo arrived and was fitted along with a 3"DP, decat, and FMIC.
Back to Bill (3 hour drive each way) for a stage 2 map. This time fuel pump flagged up as being weak, probably from the original map. Still made lowish power (260ish) to protect the shagged pump. Back again a few months later with new fuel pump and I had a nice healthy car that produced a nice figure and felt fast. Can't remember the figures.
Fast forward a bit more, I fully rebuild the engine with rods, reconditioned large port head, manifold ect ect. The original map had also claimed the lives of the K04 mani, and the head which were both severely cracked. I had moved house and RTech were 1hour 45 away compared to 3.5 hours to Bills so I thought I'd try out RTech for a custom map and the rest is history.
Anyway, sorry for the long post but my point is I've had experience of Badger5, RTech, and just a flash tuner. I live in the south east and I really do think it's worth the effort to make the journey (even a few times) to get the best service, the best advice, and the best results that your car can produce.
Bottom line is to make sure the car has a full health check prior to mapping and that you get graphs showing the fuelling after the mapping. As described above, a poor fuelling map can destroy a lost of expensive parts:
Head
Exhaust mani
Turbo
Fuel pump
That's a good £2k there which was a big learning curve for me.